The multichannel T1 Integrated Services Digital Network (ISDN) Primary Rate Interface (PRI) port adapter PA-MC-4T1 is a single-wide module that integrates channel service unit (CSU) functionality, data service unit (DSU) functionality, and T1 channel support into the Cisco router. The PA-MC-4T1 provides four independent T1 (100-ohm) connections via RJ-48C connectors. This T1 port adapter can provide up to 128 separate full-duplex HDLC fractional or full T1 channels.